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Empirical modelling of 2205 DSS flow curves using strain-compensated Arrhenius rate-type constitutive model
(Nature Research, 2024-09-28) Gonya, Elvis M.; Siyasiya, Charles Witness; Makhatha, Mamookho E.
This work predicts, hot flow curves of 2205 DSS using strain-compensated Arrhenius rate-type constitutive model. Twenty-five (25) × Ø10 diameter × 15 mm height cylindrical samples were hot compressed at a temperature between 850 and 1050 °C at an interval of 50 °C and strain rates between 0.001 and 5 s−1, using Gleeble 1500D. After the tests, corrected flow curves were plotted followed by computation of deformations constants at various deformation conditions using steady state stress. The values of the constants were (α = 0.009708, Q = 445 kJ/mol and n = 3.7) and seemed comparable to the previous studies of DSS. Steady state predictive model was then constructed using the calculated constants and showed a reasonably good accuracy with low value of MARE = 7.78%. Furthermore, calculated strain compensated Arrhenius rate type model was used to predict flow curves at various deformation. The model had a good estimation of flow curves of flow curves at 900–1050 °C across all strain rates as reflected by MARE = 5.47%. A notable discrepancy between predicted and experimental flow stress was observed at 850 °C and across all the strain rates. A model refinement using generalised reduced gradient improved the accuracy of the model by 34.7% despite deformation conditions at 850 °C and low strain rates (0.01/ 0.1) s−1 showing minimum improvement. Further modification of Z-parameter by compensating for the strain rate improved the accuracy of the model at 850 °C/0.01 s−1/0.1 s−1. Lastly, a comparison of the current model with the other non-linear model showed that the latter was more accurate in estimation of flow curves since it relied on characteristics flow stress points controlled by underlying active deformation mechanisms.
Elicitation of security threats and vulnerabilities in Insurance chatbots using STRIDE
(Nature Research, 2024-08-02) Bokolo, Zilungile; Daramola, Olawande; wande.daramola@up.ac.za
Although chatbots are used a lot for customer relationship management (CRM), there needs to be more data security and privacy control strategies in chatbots, which has become a security concern for financial services institutions. Chatbots gain access to large amounts of vital company information and clients’ personal information, which makes them a target of security attacks. The loss of data stored in chatbots can cause major harm to companies and customers. In this study, STRIDE (viz. Spoofing, Tampering, Repudiation, Information disclosure, Denial of service, Elevation of privilege) modelling was applied to identify the data security vulnerabilities and threats that pertain to chatbots used in the insurance industry. To do this, we conducted a case study of a South African insurance organisation. The adopted methodology involved data collection from stakeholders in the insurance organisation to identify chatbot use cases and understand chatbot operations. After that, we conducted a STRIDE-based analysis of the chatbot use cases to elicit security threats and vulnerabilities in the insurance chatbots in the organisation. The results reveal that security vulnerabilities associated with Spoofing, Denial of Service, and Elevation of privilege are more relevant to insurance chatbots. The most security threats stem from Tampering, Elevation of privilege, and Spoofing. The study extends the discussion on chatbot security. It fosters an understanding of security threats and vulnerabilities that pertain to insurance chatbots, which is beneficial for security researchers and practitioners working on the security of chatbots and the insurance industry.
Electrocapacitive removal of Na and Cd ions from contaminated aqueous solution using Fe3O4-poly (3,4-ethylenedioxythiophene) poly(styrene sulfonate) modified chitosan nanosheets
(Nature Research, 2024-11-15) Saliu, Oluwaseyi D.; Leping, Omphemetse; Yusuf, Tunde Lewis; Adeniyi, Adewale G.; Ramontja, James
Chitosan nanosheets (NS) stabilized on poly (3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT: PSS) was functionalized using Fe3O4 to capacitively remove chloride ions and toxic cadmium ions at optimized pH, concentration, and number of charging cycles. The synthesis procedure was investigated by Fourier transform infrared spectroscopy (FTIR), X-Ray Diffractometer (XRD), Transmission Electron Microscope (TEM), Scanning Electron Microscope – Energy Dispersive X-ray Spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET). The analyses confirms increase in surface area of the nanocomposite from 41 to 132 m2/g and a decrease in crystallinity from 75.3 to 66.9% after nanosheet formation. The highest sorption exchange capacity (SEC) for this work, 93% CdCO3 removal is achieved at 100 CDI cycles while 82% NaCl removal was achieved at 80 cycles. The SEC% increased with pH during Na ion deionization and decreased with pH during Cd removal. The works shows that chitosan is able to impart advanced structural properties to Fe3O4 and PEDOT and is able to reduce reverse migration of ions from electrodes to bulk solution, leading to higher SEC performance.
Investigation of the antimycobacterial activity of African medicinal plants combined with chemometric analysis to identify potential leads
(Nature Research, 2024-06-25) Moyo, Phanankosi; Ofori, Michael; Bodede, Olusola S.; Wooding, Madelien; Khorommbi, Ndivhuwo Kevin; McGaw, Lyndy Joy; Danquah, Cynthia A.; Maharaj, Vinesh J.; vinesh.maharaj@up.ac.za
The emergence of drug-resistant Mycobacterium tuberculosis strains is a threat to global health necessitating the discovery of novel chemotherapeutic agents. Natural products drug discovery, which previously led to the discovery of rifamycins, is a valuable approach in this endeavor. Against this backdrop, we set out to investigate the in vitro antimycobacterial properties of medicinal plants from Ghana and South Africa, evaluating 36 extracts and their 252 corresponding solid phase extraction (SPE) generated fractions primarily against the non-pathogenic Mycobacterium smegmatis and Mycobacterium aurum species. The most potent fraction was further evaluated in vitro against infectious M. tuberculosis strain. Crinum asiaticum (bulb) (Amaryllidaceae) emerged as the most potent plant species with specific fractions showing exceptional, near equipotent activity against the non-pathogenic Mycobacterium species (0.39 µg/ml ≤ MIC ≤ 25 µg/ml) with one fraction being moderately active (MIC = 32.6 µg/ml) against M. tuberculosis. Metabolomic analysis led to the identification of eight compounds predicted to be active against M. smegmatis and M. aurum. In conclusion, from our comprehensive study, we generated data which provided an insight into the antimycobacterial properties of Ghanaian and South African plants. Future work will be focused on the isolation and evaluation of the compounds predicted to be active.
Synthesis of an 8-membered oxygen-containing benzo-fused heterocycle using flow technologies - an exercise in undertaking research with sustainability as a driver
(Royal Society of Chemistry, 2025-03) Currie, Bernice Mercia; Neyt-Galetti, Nicole C.; Olivier, Tanya; Van der Merwe, Petra; Dibokwane, Lerato Shirley; Reinhardt, Anshe Michelle; Van Wyk, Lorinda T.; Panayides, Jenny-Lee; Riley, Darren Lyall; darren.riley@up.ac.za
Due to their natural abundance and biological properties, benzo-fused heterocycles are attractive targets in the field of drug discovery. Previously, a synthetic strategy for accessing 5-, 6-, 7- and 8-membered oxygen-containing benzo-fused heterocycles with the oxygen atom in the less commonly encountered 2-position was reported, however, the approach was hindered by long reaction times and a reliance on high boiling point solvents such as DMF. Targeting an 8-membered analogue as an exemplar, we highlighted that the adoption of basic green chemistry principles coupled with the use of flow chemistry techniques could be utilised (with limited development time) to improve day-to-day sustainability when performing synthetic research. In the case in hand, several key improvements were noted including (i) a higher overall yield (37% vs. 26%), (ii) a significantly reduced reaction time (110 min vs. 136 h) and (iii) the avoidance of the undesirable solvent DMF.